The invention relates to a fluid-powered impact vibrator, in particular a hydraulic hammer, comprising a fluid-powered percussion hammer or striking tool with a percussion piston, the back and forth movement of which is effected by a control arrangement, as well as a guide unit on which the percussion hammer is supported, and wherein the impact vibrator is additionally provided with a control valve, designed to function as a pressure monitor for adapting the system to the supplied input power.
Fluid-powered impact vibrators—used in particular for crushing rock, concrete or other building materials—for the most part are used as accessory units or attachments for construction machinery, e.g., excavators, loaders or other basic equipment.
Such an application case is illustrated and described, for example, in the German published patent application DE 40 36 918 A1, wherein the impact vibrator is attached to the jib of a fluid-powered excavator and is connected via an input pressure line as well as a return-flow line to the supply unit for the fluid-powered excavator.
The guide unit supporting the percussion hammer itself can be designed to function as its housing (hammer box) or also in the form of a support frame.
The percussion piston movement in the operating or working stroke direction or the opposite, return stroke direction is effected by a control means or arrangement that is associated with or integrated into the percussion hammer. In particular, the control means can be provided with a spool valve acting upon two annular percussion piston surfaces of different size, which are located in opposite movement direction, such that the smaller annular surface (effective in the return stroke direction) is always connected to the input pressure line, and the larger annular surface (effective in the operating stroke direction) is connected via the spool valve alternately to the pressure line and the return-flow line.
Owing to the fact that the hydraulic fluid supplied to the construction machinery, which fluid provides the input power for the subsequently connected impact vibrator, is designed for the internal power demands of the construction machinery itself, a retrofitting with control mechanisms is required in each case to start up the impact vibrator, so as to adapt the subsequently-connected impact vibrator to the supply unit of the respective construction machine, in particular with respect to the operating pressure. This retrofitting can be very involved and also takes for granted that suitable control mechanisms are available in each case.
The European published patent application EP 0 752 297 A2 already discloses a fluid-powered impact vibrator of the generic type, having a control valve for adapting the impact vibrator to an excessively small hydraulic mass flow, so as to ensure the necessary single-impact energy for the material crushing. This control valve, which is spring-activated and is integrated into the percussion hammer itself, reduces the number of impacts by increasing the outflow resistance, thus resulting in an adaptation to the supplied operating fluid mass flow.
The known suggestion for a solution results in an adaptation to the available input power, but only under the aforementioned circumstances, wherein the power for which the impact vibrator is designed cannot be utilized. If an excessive amount of input power is supplied, the control valve is not effective as adaptation arrangement, so that the construction machinery itself that supplies the input power must be additionally retrofitted, as mentioned above.
It is the object of the invention to provide a fluid-powered impact vibrator of the aforementioned generic type such that it can be used for construction machinery having differently designed supply units, without requiring an additional retrofitting with control mechanisms. In other words, the impact vibrator itself should be designed such that its percussion hammer—independent of the input power made available by the associated supply unit—is secured against intolerable operating conditions, such as excessive stress.